Recently, multimedia is easy to obtain for people. The source of multimedia can be, for example, a television program, a movie, a video compact disk (VCD), or a digital video disk (DVD). In these sources, the images mainly have two categories. One is non-interlaced images, which are shown line by line, and the other is interlaced images, which are shown in alternate lines. These images are primarily decoded in accord with the MPEG-2 standard.
In the process for encoding/decoding MPEG-2 images, one general processing method is to de-interlace the content of the interlaced film. Of these, WEAVE and BOB methods are common ways for de-interlacing. The WEAVE method merges two information fields to form a frame and the BOB method use a single information field to form a frame.
Obviously, the frame formed via the WEAVE method has more information and is clearer. The frame formed via the BOB method is more vague and some static portions will jiggle, such as the logo of the television station.
Certainly, the WEAVE method also has drawbacks. While macro block (MB) data are interlaced, the motions portions in the frame formed via the WEAVE method usually have some flaws with comb shapes, which are called mice teeth.
To a certain extent, the advantages of these two methods can be combined. The BOB method is used to eliminate the mice teeth in the motion portions and the WEAVE method is used to make the static portions clearer. This kind of method is called motion adaptive de-interlacing.
The algorithm disclosed in U.S. Pat. No. 6,269,484, named “method and apparatus for de-interlacing interlaced content using motion vectors in compressed video stream,” employs motion vectors and some motion estimation remains of an MPEG stream to determine if an MB is active. In fact, the motion estimation algorithm employed in the MPEG decoder is used to search for an MB most similar to a reference picture to obtain the optimum compression ratio. In other words, the motion estimation algorithm isn't used to determine if a current MB is originally active. Hence, simply using some results obtained via this algorithm, e.g. the motion vectors and motion estimation remains of the MPEG stream, to determine if a current MB is active is not reliable.
Reference is made to FIG. 1, which is a block diagram of a conventional de-interlacing system for de-interlacing interlaced content using motion vectors in a compressed video stream. FIG. 1 is a representative diagram of the U.S. patent mentioned above, which includes: an MPEG-2 interlaced picture data encoder 10, an encoded compressed MPEG-2 video stream 102, an MPEG-2 de-interlacing device 104, an MPEG-2 data stream decoder 106, an MPEG-2 decoder with motion vector extractor 108, a motion vector based deinterlacing determinator 110, a motion vector based de-interlacing bitmap 112, a block data subset 114, decoding motion vector data 116, picture data 118, a de-interlacing video rendering unit using motion vector based de-interlacing bitmap 120 and a progressive display 122.
The MPEG-2 interlaced picture data encoder 10 is an MPEG-2 encoder, which is used for decoding the interlaced picture data according-to MPEG-2 standard and passing the encoded compressed MPEG-2 video stream 102 to the MPEG-2 de-interlacing device 104. The MPEG-2 de-interlacing device 104 includes the MPEG-2 data stream decoder 106 and de-interlacing video rendering unit using motion vector based de-interlacing bitmap 120. The MPEG-2 data stream decoder 106 includes the MPEG-2 decoder with motion vector extractor 108, motion vector based de-interlacing determinator 110 and motion vector based de-interlacing bitmap 112.
The MPEG-2 decoder with motion vector extractor 108 generates the block data subset 114 and decoding motion vector data 116 during decoding and passes them to the motion vector based de-interlacing determinator 110. The motion vector based de-interlacing determinator 110 produces the motion vector based de-interlacing bitmap 112, which has two bits provided to indicate if each MB of a picture is a motion portion or motionless portion.
The MPEG-2 decoder with motion vector extractor 108 produces and passes the picture data 118 to the de-interlacing video rendering unit using motion vector based de-interlacing bitmap 120. Then, the processed picture is shown on the progressive display 122.
Accordingly, the conventional de-interlacing system and method mentioned above still have some drawbacks that could be improved. The present invention aims to resolve the drawbacks in the prior art.